The present invention relates to a biocompatible composite material which exhibits excellent tissue adhesion, outstanding biocompatibility, moldability, trimability and flexibility and to prostheses and reconstructive sheeting comprising such a material.
One material in use for reconstruction of tissue deformities is silicone. Silicone is a soft, pliable material which is easily molded to custom shapes and can be easily deformed during positioning of a prosthesis made therefrom. However, silicone has less than optimum biocompatibility. Moreover, it is difficult to anchor a prosthesis made from silicone due to its poor tissue adhesion. Therefore, silicone prostheses must be fixed by sutures and/or texturing the silicone surface to promote mechanical tissue adhesion.
Hydroxylapatite, on the other hand, exhibits the ability to form a tight bond with surrounding tissues. However, hydroxylapatite is a ceramic material and is, therefore, very brittle and somewhat difficult to form into usable shapes.
U.S. Pat. No. 4,192,021 to Deibig et al discloses bone replacement or prosthesis anchoring material on the basis of sintered calcium phosphates which consists of a mixture of calcium phosphates with low- or high-molecular weight organic substances. More specifically, the anchoring material consists of a mixture of calcium phosphates composed of CaO and P.sub.2 O.sub.5 in a quantitative ratio of 2:1 to 4:1 with biodegradable polymers in a ration of 10:1 to 1:1 of phosphate to polymer and is implantable as a solid body. A method for the production of the material is disclosed wherein calcium phosphate with a porosity of 15 to 30 volume percent is used and its pores are filled by impregnation with polymer material.
U.S. Pat. No. 4,222,128 to Tomonaga et al discloses a composite implant material comprising a sintered apatite material and a thermoplastic or thermosetting resin. The composite material is prepared by forming a sintered apatite material and filling or impregnating a thermoplastic or thermosetting resin into the pores or holes of the sintered apatite material, which have been formed during the formation of the sintered material or perforated after the formation thereof. However, while this patent discloses the composite implant material to have excellent physical strength, the material cannot be molded or easily trimmed to custom shapes by the physician.
U.S. Pat. No. 4,645,503 to Lin et al discloses a moldable bone-implant material containing between about 65 to 95% hard filler particles and a binder composed of between about 35 to 5% of a biocompatible, biodegradable, thermo-plastic polymer which has fluidic flow properties at or below about 60.degree. C. One preferred binder is polylactic acid having a molecular weight between 400 and 5,000 daltons, and a preferred hard filler is hydroxylapatite. In use, the material is warmed to a temperature which allows molding, and the bone site is filled with the moldable material which then forms a contour-fitting, semi-rigid implant. The implant retains its contour fit and acquires a rigid final state as the binder in the implant is gradually biodegraded and replaced through tissue ingrowth from the surrounding bone site. However, this material is intended to be semi-rigid rather than flexible, and is made to resorb after a period of time rather than remain indefinitely. In addition, the polylactic acid tends to resorb too rapidly, causing inflammation.
U.S. Pat. No. 4,636,526 to Dorman et al discloses composites of unsintered calcium phosphates and synthetic biodegradable polymers useful as hard tissue prosthetics. The composite materials may be ground and blended with a compatible water-soluble pore-forming agent and then molded to form dense, shaped objects which may be made porous by leaching out the water-soluble pore-forming agent. The composites may be used as hard tissue prosthetics either alone or in conjunction with conventional prostheses. The polymers in the composites of the invention of Dorman et al are biocompatible synthetic polymers which are biodegradable.
U.S. Pat. No. 4,610,693 to Niwa et al discloses an implanting article molded by centrifugal dispersion and the method for producing the same. The implanting article includes a base body comprised of a mother material and a surface portion containing dispersed apatite particles. The base body and the surface portion are formed in a mold by solidifying the mother material containing apatite particles under centrifugal force. As the mother material, metals such as aluminum and aluminum alloys and synthetic resin may be employed. As the synthetic resin, phenol resin, polyester resin, urethane resin, epoxy resin, fluororesin, polysulfonic resin, polyethylene resin, polyamide resin, polypropylene resin, polyvinyl chloride resin, polycarbonate resin, polymethyl methacrylic resin, a mixture thereof and a co-polymer composed of two or more of polymerizable monomers can be used.
U.S. Pat. No. 4,693,896 to Vit et al relates to a method of processing sinterable powders into sintered ceramic products and to forms of aluminum oxide, hydroxylapatite, and tricalcium phosphate ceramic products. A preferred dental restorative composition of Vit et al comprises about 5% up to about 90% by weight of hydroxylapatite ceramic dispersed within about 10% to about 95% by weight of an orally compatible binder. Suitable binders include inorganic binders such as a binder comprised of plaster of paris and water. Alternative binding materials include polymeric or polymerizable materials in combination with the appropriate additives for hardening the binder, e.g., cross-linking agents, polymerization catalysts, diluents, etc. The polymeric or polymerizable binder may be selected from a broad group of known polymeric materials suitable for use in the oral cavity. Such materials include, for example, polymethacrylates such as hydroxyethyl methacrylate, polymethyl methacrylate, as well as other polyacrylic acids or esters, epoxy resins, polyesters, etc.
U.S. Pat. No. 4,719,918 to Bonomo et al and U.S. Pat. No. 4,684,370 to Barrett disclose use of hydroxylapatite for alveolar ridge augmentation.
U.S. Pat. No. 4,365,356 to Broemer et al relates to prosthesis parts which are obtained by providing a material as used for prostheses with an enamel or enamel-like coating and incorporating in the enamel layer, while in a viscous state, a bio-active material.
Japanese Laid-Open Patent Publication No. 281954/87 discloses a device having a through-hole therein for permitting communication between the inside and outside of a living body. The substrate of the device is formed of a polymeric material such as polypropylene, silicone rubber, fluorine resin or polyurethane, and a calcium phosphate-type compound and/or a ceramic powder is caused to exist at least on the outside surface of the material which makes contact with biological tissue. However, this document relates to a device for permitting communication between the inside and outside of a living body, i.e., a percutaneous device, and does not relate to a prosthesis or to reconstructive sheeting and, in particular, does not relate to a prosthesis for subcutaneous, middle ear or nasal implantation in a living body.
Therefore, it is still desired to provide a biocompatible composite material suitable for use as a non-percutaneous prosthesis or reconstructive sheeting which exhibits excellent tissue adhesion, outstanding biocompatibility, moldability, trimability and flexibility. It is also desired to provide such a biocompatible composite material, non-percutaneous prostheses and reconstructive sheeting which are non-resorbable.